Center camshaft scroll pump

ABSTRACT

A scroll pump includes a first scroll member having a first involute, a second scroll member scroll member having a second involute, and a camshaft rotatably connected to the first scroll member and to the second scroll member. A link is pivotably connected to the first scroll member and the second scroll member. The first and second scroll members cooperate to define a working volume wherein a working fluid is pressurized during operation of the scroll pump. The second scroll member is configured to equalize pressure across first and second opposed surfaces of an end plate thereof. The second scroll member includes a piston and cavity configured to bias the second scroll member toward the first scroll member in response to pressure across the first and second opposed surfaces of the end plate of the second scroll member.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit under 35 U.S.C. § 119 of U.S.Provisional Patent Application 63/179,967, filed Apr. 26, 2021, thedisclosure of which is incorporated in its entirety by reference herein.

BACKGROUND AND SUMMARY OF THE DISCLOSURE

Scroll pumps are known in the art. A scroll pump typically includesfirst and second scroll members having respective, interleaved, firstand second involutes. Typically, the first and second scroll members areconnected by three camshafts and an eccentric drive mechanism configuredto move the second scroll member through an orbital path with respect tothe first scroll member.

In such a scroll pump, the movement of the second scroll member withrespect to the first scroll member may be constrained at as many as fourpoints, namely, the three camshafts and the eccentric drive mechanism.This high level of constraint requires precise fabrication and assemblyof the foregoing components in order to control interference among theseveral points of constraint, which interference may result ininefficiency, high rate of wear, and other concerns during operation ofthe pump.

Also, pressure build up within the working volume of a scroll pumpinherently tends to force the first and second scroll members apart fromeach other axially. Typically, this phenomenon is mitigated byobservance of precise tolerances in the fabrication and assembly of thescroll members and camshafts. Over time, however, the foregoingcomponents can wear outside of the tolerances and thereby lessen theefficiency of the scroll pump.

The present disclosure is directed to a scroll pump with fewer points ofconstraint to reduce complexity in fabrication and assembly, andconfigured to compensate for working pressure tending to axiallyseparate the first and second scroll members to thereby reduce wear andimprove the pump's operating efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an upper perspective view of an illustrative center camshaftscroll pump according to the present disclosure;

FIG. 2 is a top plan view of the center camshaft scroll pump of FIG. 1;

FIG. 3 is a front cross-sectional elevation view of the center camshaftscroll pump of FIG. 1 taken through section A-A;

FIG. 4 is an enlarged cross-sectional front elevation view of a portionof the center camshaft scroll pump of FIG. 1 taken through section B-B;

FIG. 5A is a perspective view of a first side of an orbiting scrollmember of the center camshaft scroll pump of FIG. 1;

FIG. 5B is a perspective view of a second side of an orbiting scrollmember of the center camshaft scroll pump of FIG. 1;

FIG. 6 is a perspective view of a first side of a fixed scroll member ofthe center camshaft scroll pump of FIG. 1;

FIG. 7 is a first exploded perspective view of the center camshaftscroll pump of FIG. 1; and

FIG. 8 is a second exploded perspective view of the center camshaftscroll pump of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

The drawings show an illustrative embodiment of a scroll pump 10according to the present disclosure. The scroll pump 10 includes: afirst (or fixed) scroll member 12; a second (or orbiting) scroll member14; a camshaft 16 having a first shaft portion 16A and a second shaftportion 16B connected to, spaced from, and parallel to the first shaftportion 16A; a link 18; and a prime mover 20, for example, an electricmotor. The first scroll member 12 is in orbiting engagement with thesecond scroll member 14. The first shaft portion 16A of the camshaft 16is rotatably connected to the first scroll member 12. The second shaftportion 16B of the camshaft 16 is rotatably connected to the secondscroll member 14. A first end 18A of the link 18 is pivotably connectedto the first scroll member 12, and a second end 18B of the link 18 ispivotably connected to the second scroll member 14. The motor 20 isconfigured to rotate the camshaft 16 with respect to the first scrollmember 12 and the second scroll member 14. The link 18 substantiallyprecludes rotation of the second scroll member 14 with respect to thefirst scroll member 12 when the camshaft 16 is rotating, so thatrotation of the camshaft 16 causes the second scroll member 14 to orbitwith respect to the first scroll member 12.

The first scroll member 12 includes a first end plate 22 and a firstinvolute 24 extending axially from a first side of the first end plate22. The first end plate 22 defines a first shaft-receiving aperture 26configured to receive the first shaft portion 16A of the camshaft 16.The first end plate 22 also defines a bearing pocket 28 extending intothe first end plate 22. In the embodiment shown, the bearing pocket 28extends toward the first side of the first end plate 22 from a secondside of the first end plate 22 opposite the first side of the first endplate 22. A first bearing 30 is received within the first bearing pocket28, for example, in press-fit engagement. A land 32 at the bottom of thebearing pocket precludes the bearing 30 from being inserted into andremoved from the bearing pocket 28 from the first side of the first endplate 22. The first bearing 30 may abut the land 32.

Alternatively, the bearing pocket 28 may extend into the first end plate22 from the first side of the first end plate 22 toward the second sideof the first end plate 22. In such an embodiment (not shown), the land32 would preclude the bearing 30 from being inserted into and removedfrom the bearing pocket 28 from the second side of the first end plate22.

In other embodiments, the first aperture 26 and the bearing pocket 28may be combined into a single feature and the land 32 may be omitted. Insuch embodiments, the first bearing 32 could be inserted into andremoved from the bearing pocket 28 from the first side of the first endplate 22 or the second side of the first end plate 22.

The first bearing 30 is configured to receive the first shaft portion16A of the camshaft 16 in rotating, bearing engagement. The firstbearing 30 may be a sealed bearing, and the interfaces among the firstend plate 22, the first bearing 30, and the first shaft portion 16A ofthe camshaft 16 may be substantially sealed interfaces so that the firstbearing 32 and the foregoing interfaces are substantially airtight.

As suggested above, the first involute 24 extends axially from the firstside of the first end plate 22 in a direction perpendicular to the firstend plate 22. A first end 24A of the first involute 24 proximate aperiphery of the first involute 24 closes upon an intermediate portionof the first involute 24. A second end 24B of the first involute 24proximate a center of the first involute 24 is free. As such, the firstend plate 22 and the first involute 24 cooperate to define a spaceconfigured to receive a second involute, as will be discussed furtherbelow. A first tip seal 24S is provided at a free surface of the firstinvolute 24 opposite the first end plate 22. The free end of the firstinvolute 24 may define a recess or groove 24G configured to receive andretain the tip seal 24S.

The first scroll member 12 defines a fluid inlet aperture or port 34proximate a periphery of the first end 24A of the first involute 24. Thefluid inlet aperture 34 is configured to admit air or another fluid intothe scroll pump 10 for pressurizing thereby. The fluid inlet port 34 mayextend through one or both of the first end plate 22 and the firstinvolute 24. The first scroll member 12 also defines a fluid outletaperture or port 36 extending through the first end plate 22 proximatethe second end 24B of the first involute 24. The fluid outlet port 36 isconfigured to discharge fluid pressurized by the scroll pump 10.

The first scroll member 12 further defines a first pivot point 38configured to receive an axle or pin 40 connecting the first end 18A ofthe link 18 to the first scroll member 12 in pivoting engagementtherewith. As shown, the first pivot point 38 may be embodied as a bossproximate the periphery of the first end plate 22 and/or radiallyoutboard of the first involute 24.

The first scroll member 12 also may include one or mounting bosses 42configured to receive fasteners (not shown) for connecting the firstscroll member 12 to another structure (not shown).

A sidewall 44 extends axially from the second side of the first endplate 22. The sidewall 44 cooperates with the first end plate 22 todefine a housing configured to receive the prime mover 20, in this casean electric motor. As shown, the sidewall 44 is monolithically formed orintegral with the first end plate 22. An end cap 46 covers the open endof the sidewall 44. A seal 48, for example, an O-ring, may be providedbetween the housing wall and the end cap so that the interior of thehousing is substantially air-tight.

The second scroll member 14 includes a second end plate 52 and a secondinvolute 54 extending from a first side of the second end plate 52. Thesecond end plate 52 defines a second shaft-receiving aperture 56extending from the first side thereof to a second side thereof oppositethe first side. The second shaft-receiving aperture 56 is configured toreceive a second bearing 58 therein, for example, in press-fitengagement. The second end plate 52 also defines one or more vent holes60 extending therethrough, proximate the center of the second end plate52, as will be discussed further below. An annular sidewall 62 extendsaxially from the second side of the second end plate 52, therebydefining a cavity 64 extending axially from the second side of thesecond end plate. The cavity 64 is configured to receive a piston 66, aswill be discussed further below. The cavity 64 may be cylindrical.

As suggested above, the second involute 54 extends from a first side ofthe second end plate 52 in a direction perpendicular thereto. A secondtip seal 54S is provided at a free end of the second involute 54. Thefree end of the second involute 54 may define a recess or groove 54Gconfigured to receive and retain the second tip seal 54S.

The second scroll member 52 further defines a second pivot point 68configured to receive a second axle or pin 70 connecting the second end18B of the link 18 to the second scroll member 14 in pivoting engagementtherewith. As shown, the second pivot point 68 may be embodied as a bossproximate the periphery of the second end plate 52.

As mentioned above, the camshaft 16 includes a first shaft portion 16Aand a second shaft portion 16B. The first shaft portion 16A defines afirst axis of rotation. The first axis of rotation is perpendicular tothe first end plate 22 and parallel to the first involute 24. The secondshaft portion 16B defines a second axis of rotation. The second axis ofrotation is perpendicular to the second end plate 52 and parallel to thesecond involute 54. The second axis of rotation is radially offset fromand parallel to the first axis of rotation. The first shaft portion 16Ais configured for connection to a drive shaft of the prime mover 20 forrotation therewith. In embodiments, the camshaft 16 may be integratedand/or monolithically formed with the drive shaft of the prime mover 20.

The second shaft portion 16B defines a circumferential groove 72configured to receive a shaft seal 74, for example, an O-ring. The shaftseal 74 is engaged between the second shaft portion 16B and an innerrace of the second bearing 58. A free end of the second shaft portion16B may define a threaded bore 76 configured to receive a fastener 78,as will be discussed further below.

The first shaft portion 16A is received within the first bearing 30 inrotating bearing engagement therewith. The second shaft portion 16B isreceived within the second bearing 58 in rotating bearing engagementtherewith. The first scroll member 12 is axially fixed to the firstshaft portion 16A. The second scroll member 14 axially floats withrespect to the second shaft portion 16B.

The first scroll member 12 is engaged with the second scroll member 14so that the first involute 24 is interleaved with the second involute54. The first tip seal 24S of the first scroll member 12 engages withthe first side of the second end plate 52 of the second scroll member 14in sealing engagement therewith. Similarly, the second tip seal 54S ofthe second scroll member 14 engages with the first side of the first endplate 22 of the first scroll member 12 in sealing engagement therewith.So assembled, the first and second scroll members 12, 14 define aworking volume V substantially bounded by the first and second endplates 22, 52 and the first and second involutes 24, 54.

With the first and second scroll members 12, 14 so assembled together, afirst exposed surface area of the second end plate 52 is exposed tofluid pressure within the working volume V. The first exposed surfacearea is defined by the surface area of the first side of the second endplate 52 normal to the second axis of rotation and radially inboard ofthe first involute 24, minus the surface area of the first side of thesecond end plate 52 normal to the second axis of rotation occupied bythe second involute 54 and covered by the first involute 24/first tipseal 24S. Put another way, the first exposed surface area is the surfacearea of the first side of the second end plate 52 that projects againstthe first side of the first end plate 22, minus the surface area of thefree end of the second involute 54 engaging the first side of the firstend plate. A second exposed surface area of the second end plate 52 isexposed to fluid pressure within the cavity 64. The second exposedsurface area is defined by the surface area of the second side of thesecond end plate 52 normal to the second axis of rotation within theconfines of the cavity 64. The second exposed surface area is greaterthan the first exposed surface area so that when both sides of thesecond end plate 52 are subjected to the same fluid pressure, the netforce on the second end plate 52 parallel to the second axis of rotationtends to bias the second scroll member 14 toward the first scroll member12, thereby compressing the first and second tip seals 24S, 54S againstthe respective second and first end plates 52, 22.

As mentioned above, the link 18 is pivotably connected to both the firstand second scroll members 12, 14. More specifically, a first portion ofthe link 18, which may be proximate a first end 18A thereof, ispivotably connected to the first scroll member 12. Similarly, a secondportion of the link 18, which may be proximate a second end 18B thereof,is pivotably connected to the second scroll member 14. So connected tothe first and second scroll members 12, 14, the link 18 allows thesecond scroll member 14 to orbit with respect to the first scroll member12, while substantially precluding rotation of the second scroll member14 with respect to the first scroll member 12. As shown in the drawings,the camshaft 16 and the link 18 are the only structures constraining theradial position of the second scroll member 14 with respect to the firstscroll member 12.

As suggested above, the piston 66 is received within the cavity 64defined by the second scroll member 14. The piston 66 defines a thirdbearing-receiving aperture 80 at the center thereof. A third bearing 82is received in the third bearing-receiving aperture 80. The thirdbearing 82 is shown as a flanged bearing received in the thirdbearing-receiving aperture from a side of the piston 66 facing away fromthe second scroll member 14. The third bearing 82 may be a sealedbearing that substantially precludes fluid flow therethrough. The piston66 also defines a groove 84 about the perimeter thereof. The groove 84is configured to receive a piston seal 86, for example, an O-ring. Thepiston seal 86 substantially precludes fluid flow between the piston 66and the cavity 64.

As shown, the piston 66 is axially retained to the camshaft 16 by a snapring 50 received within a snap ring groove 51 defined by the cam shaft16. More specifically, the piston 66 and the third bearing 82 receivedtherein are disposed between the snap ring 50 and the second scrollmember 14. As such, the snap ring 50 limits the axial travel of thethird bearing 82 and, therefore, the piston 66, in a direction away fromthe second scroll member 14. The free end of the second shaft portion16B of the camshaft 16 may be received within the center of the thirdbearing 82. The third bearing 82 is configured to allow the camshaft 16to rotate with respect to the second scroll member 14, while the piston66 remains rotationally fixed with respect to the second scroll member14.

As shown, a first counter weight 88 may be proximate the base of thesecond shaft portion 16B of the camshaft 16, where the first shaftportion 16A of the camshaft is connected to the second portion 16B ofthe camshaft 16. As shown, the first counterweight 88 is disposed withinthe interior confines of the first involute 24. A second counterweight90 may be provided proximate the free end of the second shaft portion16B of the camshaft 16. The second counterweight 90 may be connected tothe end of the camshaft 16 by a fastener 78, for example, a threadedfastener, extending into the threaded bore 76 defined by the free end ofthe second shaft portion 16B of the camshaft 16. As shown, the secondcounterweight 90 is disposed within the confines of a cavity 67 definedby the piston 66 on the side of the piston 66 opposite the second endplate 52. Each of the first and second counterweights 88, 90 isrotationally fixed to the camshaft 16 and may axially fixed thereto, aswell.

A biasing spring 92 is disposed between the second side of the secondend plate 52 and the piston 66. As shown, the biasing spring 92 is anassembly of a plurality of wave washers. In embodiments, the biasingspring 92 could be a plurality of distinct wave washers, a single wavewasher, an elastomer, or any other suitable biasing member. The biasingspring 92 preloads the second scroll member 14 away from the piston 66and toward the first scroll member 12, thereby engaging the first andsecond tip seals 24S, 54S with the respective, opposing second and firstend plates 52, 22. As shown, the biasing spring 92 is disposed betweenthe second end plate 52 and the second counterweight 90. In embodiments,the biasing spring 92 could be disposed between the piston 66 and thesecond counterweight 90.

An end cap 94 covers the cavity 67 and the piston 66 and secondcounterweight 90 received therein. An end cap seal 96, for example, anO-ring, may be provided between the end cap 94 and the second scrollmember 14.

In use, the biasing spring 92 preloads the second scroll member 14toward the first scroll member 12, thereby engaging the first and secondtip seals 24S, 54S with the respective, opposing second and first endplates 52, 22. The prime mover 20 rotates the camshaft 16. The rotatingcamshaft 16 causes the second scroll member 14 to orbit with respect tothe first scroll member 12. The orbiting of the second scroll member 14with respect to the first scroll member 12 causes the air or anotherfluid to be drawn into the working volume V through the fluid inlet port34 and pumped toward the fluid outlet port 36, thereby increasing thepressure of the fluid from the fluid inlet port 34 to the fluid outletport 36.

In the absence of the vent holes 60 defined by the second end plate 52,the foregoing increase in fluid pressure acting against the first endplate 22 and the first exposed surface of the second end plate 52 wouldtend to force the first and second scroll members 12, 14 apart from eachother axially. Axial displacement of the second scroll member 14 awayfrom the first scroll member 12 resulting from such force could lessenthe effect of the first and second tip seals 24S, 54S, therebydecreasing the efficiency of the scroll pump 10.

The vent holes 60 mitigate this phenomenon by equalizing the fluidpressure on the first and second opposed sides of the second end plate52 and by applying this equalized pressure to the surface of the piston66 facing the second end plate 52 (and to the piston seal 86) in a firstembodiment or to the end cap 94 (and to the end cap seal 96) in a secondembodiment.

In the first embodiment, the equalized pressure is applied against thepiston 66. Because force equals pressure times area, because the secondexposed surface area on the second side of the second end plate 52 isgreater than the first exposed surface area on the first side of thesecond end plate 52, and because the piston 66 is fixed axially withrespect to the first scroll member 12, the net axial force acting on thesecond end plate 52 due to the fluid pressure within the working volumeV and the cavity 64 tends to bias the second end plate 52, and thereforethe second scroll member 14, toward the first scroll member 12. This netaxial force tends to increase as a function of increasing fluid pressurewithin the working volume V and the cavity 64. Also, because the secondscroll member 14 floats on the second shaft portion 16B of the camshaft16, the second scroll member 14 may be displaced slightly toward thefirst scroll member 12 in response to the foregoing axial biasing force,thereby compressing the first and second tip seals 24S, 54S against therespective, opposing second and first end plates 52, 22, and therebypromoting operational efficiency of the scroll pump 10.

In the second embodiment, as shown in FIG. 7, the piston 66 may beprovided with an optional vent hole 98 similar to vent hole(s) 60 (theoptional vent hole 98 is absent in the first embodiment). This may bedesirable where the third bearing 82 is not a sealed a bearing. Inapplications where the third bearing 82 is not a sealed bearing,pressure differential across first and second sides of the third bearing82 could force grease out of the third bearing 82, potentially leadingto premature wear and failure of the third bearing 82. Providing thevent hole 98 in the piston 66 allows for pressure equalization acrossthe piston 66, thereby mitigating against forcing grease out of thethird bearing 82 due to pressure differential across the third bearing82. In such embodiments, the equalized pressure across the second endplate 52 and the piston 66 bears against the end cap 94 and the end capseal 96. In such embodiments, in use, the second scroll member 14 isbiased toward the first scroll member 12 in a manner similar to thatdescribed above.

In any of the foregoing embodiments, cooperation of the piston 66 withthe cavity 64 may provide radial support for the second shaft portion16B of the camshaft.

The foregoing description and corresponding drawings refer to one ormore illustrative embodiments of a scroll pump according to the presentdisclosure. These embodiments are illustrative, and not limiting. Oneskilled in the art would recognize that the disclosed embodiments couldbe modified in numerous ways without departing from the scope of theinvention as defined by the appended claims.

1. A scroll pump comprising: a first scroll member, the first scrollmember comprising a first end plate and a first involute extending in anaxial direction from a first side of the first end plate; a secondscroll member engaged with the first scroll member, the second scrollmember comprising a second end plate and a second involute extending inan axial direction from a first side of the second end plate, whereinthe first involute is interleaved with the second involute; a linkpivotably connected to the first scroll member and pivotably connectedto the second scroll member, and a camshaft having a first shaft portionhaving a first axis of rotation, the first shaft portion rotatablyconnected to the first scroll member, the camshaft further having asecond shaft portion connected to the first shaft portion, the secondshaft portion having a second axis of rotation parallel to and radiallyoffset from the first axis of rotation, the second shaft portionrotatably connected to the second scroll member, wherein rotation of thecamshaft causes the second scroll member to travel in an orbital pathwith respect to the first scroll member, thereby causing the secondinvolute to travel in an orbital path with respect to the firstinvolute.
 2. The scroll pump of claim 1 wherein: the first scroll membercomprises a first pivot point; the second scroll comprises a secondpivot point; a first portion of the link is pivotably connected to thefirst pivot point; and a second portion of the link is pivotablyconnected to the second pivot point.
 3. The scroll pump of claim 2wherein the link substantially precludes rotation of the first scrollmember with respect to the second scroll member.
 4. The scroll pump ofclaim 3 wherein the first pivot point is located radially outward of thefirst involute.
 5. The scroll pump of claim 3 wherein the second pivotpoint is located radially outward of the second involute.
 6. The scrollpump of claim 3 further comprising a motor connected to and configuredto rotate the first shaft portion of the camshaft.
 7. The scroll pump ofclaim 1 wherein the first scroll member defines a first bearing pocketconfigured to receive from a second side of the first end plate oppositethe first side of the first end plate, and not from the first side ofthe first end plate a first bearing configured to receive the firstshaft portion of the camshaft in rotating engagement therewith.
 8. Thescroll pump of claim 1 wherein the first involute is in sealedengagement with the second end plate and the second involute is insealed engagement with the first end plate.
 9. The scroll pump of claim6 further comprising a first tip seal in sealing engagement with a freeaxial end of the first involute and with the second end plate.
 10. Thescroll pump of claim 9 further comprising a second tip seal in sealingengagement with a free axial end of the second involute and with thefirst end plate.
 11. A scroll pump comprising: a first scroll member,the first scroll member comprising a first end plate and a firstinvolute extending in an axial direction from a first side of the firstend plate; a second scroll member engaged with the first scroll member,the second scroll member comprising a second end plate and a secondinvolute extending in an axial direction from a first side of the secondend plate, wherein: the first involute is interleaved with the secondinvolute, rotation of the camshaft causes the second scroll member totravel in an orbital path with respect to the first scroll member,thereby causing the second involute to travel in an orbital path withrespect to the first involute, the second end plate has a first side andsecond side opposite the first side, the second side of the second endplate defines a cavity having a sidewall, and the second end platedefines a vent hole extending therethrough from the first side thereofto the second side thereof so that the cavity is in fluid communicationwith a working volume defined by cooperation of the first involute andthe second involute, the scroll pump further comprising a pistonreceived within and in sealed engagement with the sidewall of thecavity, wherein the piston axially fixed to the second shaft portion ofthe camshaft.
 12. The scroll pump of claim 11 wherein the first side ofthe second end plate defines a first exposed surface area facing thefirst end plate and wherein the second side of the second end platedefines a second exposed surface area within the cavity.
 13. The scrollpump of claim 12 wherein the second exposed surface area is greater thanthe first exposed surface area.
 14. The scroll pump of claim 13 whereinthe second scroll member floats axially with respect to the first scrollmember and the camshaft.
 15. The scroll pump of claim 14 wherein fluidpressure within the working volume and the cavity exerts a net axialforce on the second end plate and wherein the net axial force biases thesecond end plate axially toward the first end plate.
 16. The scroll pumpof claim 15 wherein a first face of the piston facing the second endplate is exposed to the fluid pressure and not a second face of thepiston opposite the first face is not exposed to the fluid pressure. 17.The scroll pump of claim 15 wherein the piston is sealingly enclosedwithin the cavity, and wherein the piston defines a second vent hole.18. The scroll pump of claim 17 wherein a first face of the pistonfacing the second end plate and a second face of the piston opposite thefirst face are exposed to the fluid pressure.
 19. The scroll pump ofclaim 11 further comprising a biasing spring configured to bias thesecond scroll member toward the first scroll member.
 20. The scroll pumpof claim 19 further comprising a first tip seal disposed between thefirst scroll and the second end plate and a second tip seal disposedbetween the second scroll and the first end plate.
 21. The scroll pumpof claim 20 wherein the biasing spring is configured to preload thesecond scroll member against the fixed scroll member to sealingly engagethe first tip seal with the second end plate and sealingly engage thesecond tip seal with the first end plate.
 22. The scroll pump of claim19 wherein the biasing spring is disposed between the moving scrollmember and the piston.